Nowadays, a fingerprint function gradually becomes a new hotspot for a smartphone. An active fingerprint sensor has long-distance recognition and can penetrate a relatively thick coating, and practicality and reliability are relatively high. When the active fingerprint sensor works, a high-frequency voltage of a stimulus source reaches a finger through stainless steel, so that a radio frequency field is formed between the finger and the sensor. The sensor includes a sensor array. Because a fingerprint of a finger is concave and convex, and effects of a convex area and a concave area on the radio frequency field are different, signal strength sensed by the sensor array has a peak value in the convex area and a valley value in the concave area. After values of signal strength sensed by sensor elements in the sensor array are compared with a reference stimulus high-frequency signal, a signal is amplified by using an amplifier. A finger concave and convex image on the entire array is correspondingly obtained, that is, a fingerprint image.
In the prior art, there is a fingerprint recognition apparatus in which an active fingerprint sensor is used and a stainless steel frame is used, to generate a radio frequency signal.